From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9C0BC43141 for ; Wed, 20 Jun 2018 22:36:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F9CB20652 for ; Wed, 20 Jun 2018 22:36:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QVs9RZqe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F9CB20652 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933824AbeFTWgw (ORCPT ); Wed, 20 Jun 2018 18:36:52 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:52394 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933555AbeFTWgu (ORCPT ); Wed, 20 Jun 2018 18:36:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To: Subject:Sender:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=dRKbFl2LYWJbXvt+Skk6o6oKbyqiJEAC2vudTvQv09g=; b=QVs9RZqe8irJkY1c8lPa6jIKr d55/71p/fxPOsdQl8c3brfkq34Eo7WifezavF0tJxWLAFdrbyhIgowcD6GeTxktpOaZR4CmwicOkE hVKHoxkkHqMOfjpAfas2up3WaVCveQjUCtacW1r/FOO+QoCzD+ssV4zu6cu68elSJle8hM6JH4IfV BdZsiJHvOvoXtjzbqRz86dcEpPgXWchyo82PZovd5EZQYWic8VSXNnSZ3MT+MMPVvwfVohQxSDvuQ qW58nRsBX2ZZ1WA9ZtLbkWK4UZD9t6x6OU9HJCSSE7iB/0tkua9EmqomInrHlYg6uwRXOuoeQXYv4 8/JL1ki7Q==; Received: from static-50-53-52-16.bvtn.or.frontiernet.net ([50.53.52.16] helo=dragon.dunlab) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fVliZ-0005Vj-EI; Wed, 20 Jun 2018 22:36:47 +0000 Subject: Re: [PATCH v8 4/4] vsprintf: Add command line option debug_boot_weak_hash To: "Tobin C. Harding" Cc: Theodore Ts'o , Linus Torvalds , Steven Rostedt , Kees Cook , Anna-Maria Gleixner , Andrew Morton , Greg Kroah-Hartman , Arnd Bergmann , Andy Shevchenko , linux-kernel@vger.kernel.org References: <20180620042046.30806-1-me@tobin.cc> <20180620042046.30806-5-me@tobin.cc> <20180620223014.GE11671@eros> From: Randy Dunlap Message-ID: Date: Wed, 20 Jun 2018 15:36:44 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180620223014.GE11671@eros> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/20/2018 03:30 PM, Tobin C. Harding wrote: > On Wed, Jun 20, 2018 at 09:09:49AM -0700, Randy Dunlap wrote: >> On 06/19/2018 09:20 PM, Tobin C. Harding wrote: >>> Currently printing [hashed] pointers requires enough entropy to be >>> available. Early in the boot sequence this may not be the case >>> resulting in a dummy string '(____ptrval____)' being printed. This >>> makes debugging the early boot sequence difficult. We can relax the >>> requirement to use cryptographically secure hashing during debugging. >>> This enables debugging while keeping development/production kernel >>> behaviour the same. >>> >>> If new command line option debug_boot_weak_hash is enabled use >>> cryptographically insecure hashing and hash pointer value immediately. >>> >>> Signed-off-by: Tobin C. Harding >>> Reviewed-by: Steven Rostedt (VMware) >>> --- >>> Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ >>> lib/vsprintf.c | 17 +++++++++++++++++ >>> 2 files changed, 26 insertions(+) >>> >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >>> index 638342d0a095..a116fc0366b0 100644 >>> --- a/Documentation/admin-guide/kernel-parameters.txt >>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>> @@ -748,6 +748,15 @@ >>> >>> debug [KNL] Enable kernel debugging (events log level). >>> >>> + debug_boot_weak_hash >>> + [KNL] Enable printing pointers early in the boot >>> + sequence. If enabled, we use a weak hash instead of >>> + siphash to hash pointers. Use this option if you need >>> + to see pointer values during early boot (i.e you are >> >> maybe: >> to see hashed pointer values >> i.e., not raw pointers. > > You cannot see 'raw pointers' anyways? only if using %px ? Maybe it's just terminology. I don't consider a hashed value as a pointer value. It's just a key or handle or some other number, but it's not a pointer. >> >>> + seeing instances of '(___ptrval___)'). >>> + Cryptographically insecure, please do not use on >>> + production kernels. > > thanks for the review, I don't quiet see how to use your suggestion to > make the text clearer. If you still feel this change is needed perhaps > you could write so I understand i.e 'Use this option if ...' OK, if you are good with it, I am too. :) thanks, -- ~Randy